Page 586 - Clinical Application of Mechanical Ventilation

552 Chapter 17

NASAL CPAP

Some infants may be able to ventilate satisfactorily but unable to maintain suffi-
cient oxygenation in spite of traditional oxygen therapy. If the hypoxemia is due to
mild to moderate intrapulmonary shunting and the spontaneous breathing effort
is adequate and sustainable, this type of hypoxemia may be corrected by applying
airway pressure alone, without the need for mechanical ventilation. Continuous
positive airway pressure (CPAP) is the method to apply airway pressure without
any mechanical breaths. For the neonatal population, indications for CPAP in-
clude respiratory distress syndrome (RDS), apnea of prematurity, obstructive sleep
apnea (OSA), viral bronchiolitis, aspiration pneumonia, meconium aspiration syn-
drome (MAS), congestive heart failure (CHF), transient tachypnea of the newborn
(TTN), or post-operatively (Walsh et al., 2010).

Use of Nasal CPAP

Continuous positive airway pressure (CPAP) was introduced in 1971. It reduces V/Q
mismatch by improving the functional residual capacity and reducing intrapulmo-
nary shunting. CPAP was originally administered via an endotracheal tube. Over
the years, nasal CPAP (N-CPAP) was developed and has become a less invasive
nasal CPAP (N-CPAP): A nasal
device for delivering continuous procedure to reduce the F O requirement and the need for mechanical ventilation.
I
2
positive pressure to the airway Recent publications have reported that N-CPAP is both feasible and effective in
without the need for intubation. The
neonate must have adequate and most very-low-birth-weight infants and those with acute respiratory failure. Early
sustainable spontaneous breathing rescue treatment with surfactant replacement with a brief intubation has further
effort to use nasal CPAP.
increased the effectiveness of N-CPAP (Jeena et al., 2002; Malik et al., 2003).
A bubble CPAP device creates CPAP by an underwater seal with vigorous bubbling.
Infants receiving CPAP by an underwater seal were observed to have chest vibration at
frequencies similar to high frequency ventilation (HFV). In one study, lower minute
ventilation, respiratory frequency, and better gas exchange were observed when com-
pared with ventilator-derived CPAP devices. It suggests that the chest vibrations pro-
duced with bubble CPAP may have contributed to these findings (Lee et al., 1998).
Unlike the CPAP provided by a ventilator, the flow-generating CPAP device uses
flow to maintain CPAP and has no exhalation valve. Since this CPAP device does
not have an exhalation valve, it may offer a lower resistance than the ventilator
CPAP. There are different-sized prongs and masks for better fitting on the patient.
Different-sized hats are also available for stabilization of the flow-generating attach-
ment. The expiratory limbs of the circuit hang loose and the flow is driven out the
tube opening to room air. These devices can be noisy, but the manufacturers have
produced a baffle device to reduce the noise level.
All CPAP devices should be humidified. One humidification manufacturer rec-
ommends setting temperature to 39°C because of cooling effects distal to the hu-
The initial N-CPAP set- midification system.
tings for most infants range The initial N-CPAP settings for most infants range from 4 to 7 cm H O with
from 4 to 7 cm H 2 O with flow 2
rates from 5 to 10 L/min. flow rates from 5 to 10 L/min. For infants with RDS, the CPAP level should
start at 6 cm H O. If the infant with RDS is having recurrent apnea, persistent
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